#include <bits/stdc++.h>
using namespace std;
void solve(){
	int n,m,cnt=0;
	cin>>n>>m;
	vector<int> ans,a(n),b(m);
	for(int&x:a) cin>>x;
	for(int&x:b) cin>>x;
	sort(a.rbegin(),a.rend());
	sort(b.rbegin(),b.rend());
	for(int i=0;i<m;i++){
		if(a[i]>b[i]){
			cout<<"-1\n";
			return;
		}
		cnt+=b[i]-a[i];
		if(n-cnt<m){
			cout<<"-1\n";
			return;
		}
	}
	multiset<int> s(begin(a),begin(a)+m),t(begin(a)+m,end(a));
	for(;n-cnt>m;n--){
		if(t.empty()){
			cout<<"-1\n";
			return;
		}
		int x=*t.begin();
		ans.push_back(x++);
		t.erase(t.begin());
		if(x>*s.begin()) cnt--,s.erase(s.begin()),s.insert(x),t.insert(x-1);
		else t.insert(x);
		t.erase(t.begin());
	}
	int p=0;
	for(int x:s) a[p++]=x;
	reverse(begin(a),begin(a)+m);
	for(int i=0;i<m;i++){
		if(a[i]>b[i]){
			cout<<"-1\n";
			return;
		}
		while(a[i]<b[i]) ans.push_back(a[i]++);
	}
	cout<<n-m<<"\n";
	for(int x:ans) cout<<x<<" ";
	cout<<"\n";
}
int main(){
	cin.tie(0)->sync_with_stdio(0);
	int t;
	cin>>t;
	while(t--) solve();
	return 0;
}